1. Field of the Invention
The present invention relates to an optical connector with sleeves located between optical fibers and light-receiving/light-transmitting modules and being capable of making optical contacts therebetween.
2. Description of the Related Art
A typical optical connector with sleeves located between the optical fibers and the optical-receiving/optical transmitting module is disclosed in J-UM-6-33443 by the inventors of the invention.
FIG. 17 is a horizontal sectional view of a conventional optical connector, and FIG. 18 is a horizontal sectional view of the receptacle shown in FIG. 17. In FIGS. 17 and 18, reference numeral 1 denotes a sleeve, and reference numeral 2 denotes an optical connector.
Sleeves 1 are attached to a receptacle (connector on the side of a device) constituting the optical connector 2. These sleeves 1 are arranged between optical element modules 4 (consisting of a light-receiving module and a light-emitting module) and a pair of optical fibers 6 which are attached to an optical plug (connector on the side of the optical fiber) constituting the optical connector 2, respectively. The sleeves 1 serve to make an optical connection between the light-receiving/light-transmitting modules 4 and optical fibers 6.
A more detailed explanation will be given of the optical connector 2 as well as the sleeves 1.
The optical connector 2 includes the receptacle 3 and the optical plug 5 fit into the receptacle 3.
The receptacle 3, as shown in FIGS. 17 and 18, has a housing 7 made of synthetic resin. and having a pair of housing chambers 8. The housing chambers 8 each houses a light-receiving/light transmitting module 4 which is supported by a back sheet 9 made of elastic material such as rubber. The rear of each of the housing chambers 8 is covered with a cap 10. The receptacle 3 has a pair of receiving cylinders 12 which are arranged in front of the housing chambers 8, and extended forward so as to accord with the respective axes of lenses 11. The sleeves 1 are inserted in the receiving cylinders 12, respectively. The sleeve 1 can be formed by grinding both end surfaces of the optical fiber composed of a core and a cladding (not shown) after it has been secured to a cylindrical holder 14.
On the other hand, the optical plug 5 fits in the receptacle 3, as seen from FIG. 17 and 19 which is a horizontal sectional view of the optical plug shown in FIG. 12, includes a pair of ferule assemblies 15 each covering the optical fiber with its end face exposed at the tip of the assembly, a plug housing 17 with a pair of cylindrical partitions 16 for protecting the ferule assemblies 15 housed therein, a spring cap 17 fit over the plug housing 18 and a boot 19 fit over the rear of the spring cap 18.
The plug housing 17 has shoulders 17a each to be engaged with a flange 15a formed on the. rear half of the periphery of each ferule assembly 15. The ferule 15 is urged forward normally by a spring 20 which is located between the flange 15a and inner cylinder 18a of the spring cap 18.
As shown in FIG. 19, by engagement between the flange 15a and shoulder 17a, the tipA of the ferule assembly is always pulled more internally than the tip of the plug housing 17. The tip A of the ferule assembly 15 corresponds to the light-incident/emitting face of the optical fiber 6.
As regards the above configuration, referring to FIG. 17, an explanation will be given of connection between the receptacle 3 and the optical plug 5.
When the receptacle 3 is fit over the optical plug 5, the receiving cylinders 12 advance into the plug housing 17, and the ferule assemblies 15 also advance into the receiving cylinders 12. At this time, the ferule assembly 15 is brought into contact with the tip of the receiving cylinder 12 and a suitable contact pressure is kept by the elastic force by the spring 20.
In this state, the tip A (FIG. 19) and sleeve 1 are arranged with a minimum gap (not shown) kept. Therefore, the loss of the gap can be minimized.
The prior art described above, in which the sleeve 1 has an optical fiber 13 and is formed in a ring-shape, presents the following problems.
As shown in FIG. 20, with respect to a light beam c1 (within a range of a critical angle) which is propagated through an optical fiber 6 and sleeve 1 along an optical path indicated by arrow in FIG. 20, when the light receiving face 4a of the light receiving element module 4 is smaller than the light-emitting face 1a of the sleeve 1 (the width of the module 4 is smaller by d than that of the optical fiber 13 on the one side with respect to a center line), the light beam c1 may not be received by the light receiving element module 4. This is one of causes reducing the transmission efficiency.
Therefore, by designing the optical connector so that light-receiving module 4 can receive such optical beam c1, the transmission efficiency can be improved.
Although not shown, when the light beam emitted from the light emitting face (not shown) of the light emitting element module is diffusive-LED light, part of the light cannot enter the sleeve 1.
Even if such a light beam is incident on the sleeve 1, it becomes a light beam c2 out of the critical range of angle (xcex8). Therefore, the light c2 does not reflect totally but permeates through the sleeve 1. The light c2 will be not be propagated.
Therefore, by designing the optical connector so that the light such as the light beam c2 is totally reflected, it is expected that the transmission efficiency can be improved.
Further, the prior art intends to minimize the gap loss to improve the transmission efficiency. However, a slight gap between the optical fiber 6 and sleeve 1 and axis displacement therebetween may influence the transmission efficiency.
There is also a problem relative to productivity of the sleeve 1 as well as the problem of the transmission efficiency.
Specifically, as described above, in order to improve the optical characteristic (transmission efficiency of light) of the sleeve 1, after the optical fiber 13 is inserted in and attached to the holder 14, both end surfaces of the optical fiber 13 as well as the holder 14 must be ground using abrasives of plural grain sizes. Thus, production of the sleeve 1 requires many manufacturing steps inclusive of necessary previous steps of making its components, and is inferior in productivity.
Further, production of the: sleeve 1, which requires monitoring the production status of its components and testing the size, is involved with complicate production management. This deteriorates the productivity of the sleeve and increases the production cost.
It is also demanded to assemble the sleeve with a receptacle smoothly.
An object of the invention is to provide an optical connector which can improve its transmission efficiency and enhance its productivity to reduce the production cost.
In order to attain the above object, in accordance with the present invention, there is provided an optical connector comprising a pair of optical fibers, light receiving/transmitting modules and sleeves each located therebetween and making an optical connection therebetween, wherein each the sleeves has a light guiding passage which is tapered from each the optical fibers toward the light receiving/transmitting modules, thereby forming a conical shape with an sloped side wall and a first end face having a reduced diameter of the light-guiding passage and arranged oppositely to each the light receiving/transmitting modules.
In this configuration, when the light propagated through the optical fiber is incident on the sleeve, it is propagated through the light-guiding passage while while repeating total reflection on the sloped side wall and gradually converged toward the light-receiving module.
On the other hand, the light which falls out of a critical angle in the prior art, can be transmitted through the light-guiding passage owing to its tapering. In this case, since the diameter of the light guiding passage increases in a propagating direction, the number of times of total reflection of the transmitted light can be decreased. Therefore, the sleeve does not retard the transmission speed of light. Thus, the transmission efficiency of light can be greatly improved.
Preferably, each the sleeves has a guiding portion enlarged in an direction perpendicular to an axis of the light-guiding passage to form a ring shape, the guiding portion being formed on the side of each the optical fibers integrally to the light guiding passage.
In this configuration, the provision of the guiding portion can be necessity of a holder or a particular attaching structure for the light-guiding:portion. The integral guiding portion formed integrally to the light-guiding passage removes necessity of providing any particular attachment to the housing, reduces the number of components and simplifies the manufacturing:-process. This contribute to easiness of the production management, improvement in the productivity and reduction in the production cost.
Preferably, the guiding portion has a ring-shaped groove formed on the end face opposite to each the light-receiving modules and successive to the side wall of the light guiding passage.
This configuration enlarges the range of an air layer abutting on the side wall of the light-guiding passage, and hence lengthens the range of total reflection of light in the light-guiding passage in the optical direction, thereby improving the efficiency of light.
Preferably, the guiding portion has a cylindrical-hood shape flange extending toward the each the light receiving/transmitting modules and surrounding the light guiding passage.
This configuration enlarges the range of supporting the sleeve so that the sleeve can be supported more stably by the housing. Therefore, the optical axis of the sleeve is not displaced, thereby improving the efficiency of light.
Preferably, the guiding portion has a projection formed along an extending direction of the flange and integrally thereto. The projection serves as a rotation stopper so that the sleeve does not rotate in the housing. Therefore, the sleeve can be arranged stably, thereby improving the efficiency of light.
Preferably, the pair of sleeves are coupled with each other by a coupling member. In this configuration, the connector housing 72 can be assembled by making an insertion operation only once. In addition, the provision of the coupling member improves the productivity and transmission efficiency.
Preferably, each the sleeves includes a lens integrally formed on its face on the side of the optical fiber, the lens making an optical connection with the optical fiber and being convex toward it.
In this configuration, since the lens is formed integrally to the light guiding passage, the adverse effect from the gap between the optical fiber and sleeve and displacement of the direction of the optical axis are relaxed, thereby improving the transmission efficiency of light.
Preferably, the lens is arranged so that its apex does not protrude from the end face of the guiding portion on the side of each the optical fibers.
In this configuration, the guiding portion serves as a member for protecting the lens. The sleeve, before it is assembled, can be easily managed.
The second end face of the light-guiding passage opposite to the first end face is served as a light-receiving face receiving light propagated through each the optical fibers, the light receiving face having a larger diameter of an end face of each the optical fibers which serves as a light emitting face. In this configuration, a larger amount of light can be received from the optical fiber, thereby improving the transmission efficiency of light.
Preferably, the first end face of the light-guiding passage is served as a light emitting face emitting light to be propagated toward a light receiving face of the light receiving module, the first end face having a smaller diameter than that of light receiving face.
In this configuration, a larger amount of light can be received from the light receiving module, thereby further improving the transmission efficiency of light.
Preferably, the first end face of the light-guiding passage is served as a light receiving face receiving light to be transmitted from an light emitting face of the light-transmitting module, the first end face having a larger diameter than the light emitting face.
In this configuration, a larger amount of light can be received from the light receiving module, thereby further improving the transmission efficiency of light.
Preferably, the light guiding passage is mainly made of transparent resin.
Therefore, the sleeve can be easily manufactured by injection molding. This simplifies the manufacturing process, improves the production efficiency, and reduces the production cost.
Preferably, the each the sleeves is coated with an anti-reflecting film in its light receiving face.
The anti-reflective film serves to prevent reduction in the amount of incident light, thereby further improving the transmission efficiency of light.
The above and other objects and features of the invention will be more apparent from the following description taken in conjunction with the accompanying drawings.